Gas lift system for wells



June 30, 1964 Filed Aug. 7, 1961 E. E. ROACH 3,139,040

GAS LIFT SYSTEM FOR WELLS 3 Sheets-Sheet 1 ii f/J%//7e Roar/2 m0INVENTOR.

ATTO/TVVEV June 30, 1964 E. E. RoAcH GAS LIFT SYSTEM FOR WELLS 3Sheets-Sheet 2 Filed Aug. 7 1.961

INVENTOR.

ATTOQ/VEV June 30, 1964 E. E. ROACH GAS LIFT SYSTEM FOR WELLS 3Sheets-Sheet 3 Filed Aug. 7, 1961 United States Patent 3,139,040 GASLIFT SYSTEM FDR WELLS Erskine E. Roach, Houston, Tex., assignor toHarold Brown Company, a corporation of Texas Filed Aug. 7, 1961, Ser.No. 129,861 9 Claims. (Cl. 103247) This invention relates toimprovements in the gas lift system for producing oil wells.

Current oil well completion practices are tending in the direction ofemploying small diameter well casings,

commonly referred to as slim hole or tubingless completions. The latteris something of a misnomer, as in many instances, a string of productiontubing must be run inside the casing. However, by reason of therelatively small casing, the annular clearance between the tubing andeasing becomes so small that when artificial lift becomes necessary,installation of a tubing string having the usual externally mounted gaslift valves thereon becomes impractical. This is particularly truebecause operators require that sufiicient clearance be available forpassage of wash pipe over the tubing string.

To meet this condition, pressure loaded injection valves of the tubularconcentric type, which may be mounted coaxially in the tubing string,have been designed and used with varying degree of success. These,however, have been found to be subject to various operating andmechanical difiiculties and their replacement involves removal of thetubing string with its attendant difficulties and expense.

An early gas lift system, which has been considered obsolete for anumber of years, employed a type of valve which was of telescopicconstruction adapted to be mounted coaxially in the tubing string andprovided with port means which were opened and closed in response tovertical reciprocation of the upper portion of the tubing stringrelative to the lower portion thereof, the latter being anchored in thewell bore. Reciprocation of the upper portion of the tubing string waselfected at the surface either manually or mechanically in order to openand close the valve ports. As the unloading of the well thus had to behandled manually and as there was no means for effectively seeking outand employing the most efiicient injection point with the changing wellconditions, the system fell into disrepute and, as noted, has becomeobsolete.

The present invention is directed to improvements in this early systemby which its disadvantages are overcome and the operation rendered fullyautomatic in opening and closing the valves, in controlling the supplyof injection gas, and in locating the most efiicient gas injection pointfor changing well conditions. This improved system permits the use ofvalves of the telescoping type which do have the advantages that theirexternal dimensions may be held within limits permitting their use inslim casings, and they may be made relatively simple in form and ofrugged construction. The present invention is also directed toimprovements in the form of the valve itself to improve its operation ina system of the kind herein contemplated.

The improvements contemplated by the present invention embody theemployment of a control system adapted to automatically unload a gaslift well employing the tele scoping type valves in the tubing string.

In accordance with one embodiment of this invention, the control systemcomprises a novel combination of a hydraulic actuator for reciprocatingthe upper portion of the tubing string with time cycle controls andregulators co-operating to automatically unload the production string tothe operating valve and to seek out the lowermost point at which gas canbe eifectively injected into the tubing. The gas lift system hereincontemplated may 3,139,040 Patented June 30, 1964 be employed both forintermitting wells with low production rates and for continuous flowinstallations which produce large quantities of fluids. In eitherinstallation the control system will automatically seek out the mosteflicient operating point along the valve string at time intervals asset on the time cycle control elements.

Among the other objects of this invention are the provision of a gaslift system which will operate with minimum wastage of power or liftinggas; which is relatively simple in construction; and which is highlyefficient in its operation.

Other and more specific objects and advantages will become apparent fromthe following detailed description when read in conjunction with theaccompanying drawing which illustrates useful embodiments in accordancewith this invention.

In the drawing:

FIG. 1 is a generally schematic view of the gas lift system inaccordance with one embodiment of this invention installed in a well;

FIG. 2 is a fragmentary longitudinal sectional view of the upper endportions of the well casing and flow tubing having the hydraulicactuator connected thereto;

FIG. 3 is a longitudinal sectional view of one of the gas injectorvalves with the parts in the port-closing position;

FIG. 4 is a view similar to FIG. 3 showing the valve parts in theport-opening position;

FIGS. 5 and 6 are cross-sections taken respectively along lines 55 and6-6 of FIG. 4; and

FIG. 7 is a fragmentary diagrammatic view of a modification of thesystem.

Referring first to FIG. 1, there is shown a well W lined with a casingC. A casinghead H, in any suitable form such as a T fitting, is mountedon the upper end of casing C and the center arm of the T fitting hasconnected thereto a pipe A through which power or lifting gas under highpressure may be introduced into the casing from any suitable source (notshown). Mounted in the upper end of casinghead H is an adapter nipple N.on which is mounted an upstanding cylinder L, the upper end of whichcommunicates with a discharge pipe D controlled by a master valve M, thefluid leaving valve M passing through discharge fittings F. A string ofproduction tubing T extends into the well through casing C and comprisesan upper portion U and a lower portion V connected together by aplurality of longitudinally separated telescoping couplings, eachdesignated generally by the numeral 10, which comprise the gas injectorvalves, as will be described in greater detail hereinafter. The valves10 are spaced apart by nipples G of any suitable length, as may bedetermined in the known manner for the particular installation. Lowerportion V of the flow tubing is fitted with a standing valve S ofconventional construction and is secured to the wall of easing C bymeans of a conventional anchor K to prevent longitudinal movement oflower portion V of the tubing string, and thereby permit relativereciprocation of upper portion U through relative movement between theparts of the telescoping couplings 10. Upper portion U of the tubingstring extends through adapter nipple N, which has a stufiing box,indicated at B, to seal between the tubing and the casing whilepermitting reciprocation of upper portion U. The latter has mountedabout its upper end an annular piston R which extends radially intoslidable sealing engagement with the wall of cylinder L. The upper endof tubing T is in open communication with the interior of cylinder Labove piston R so that well fluid discharging from tubing T may flow outof the upper portion of cylinder L through discharge conduit D. Forreciprocating upper portion U of the tubing string, a suit ablehydraulic pressure fluid is supplied to the interior of cylinder Lbetween stufling box B and piston R through a conduit 11 which isconnected to the discharge of a pump 12, the suction of which isconnected, by means of a suction pipe 12a, to a reservoir 13 containinga body of suitable hydraulic fluid.

Pump 12 may be of any conventional type'and preferably one driven by aconventional pneumatic motor indicated at 12b. A check valve 14 ismounted in conduit 11 and arranged to permit pressure fluid to flowtoward cylinder L but prevent return flow through pump 12 to thereservoir. A bleed pipe 15 connects at one end to conduit 11 betweencheck-valve 14 and cylinder L and at the other end to the upper portionof reservoir 13. A bleed valve 16, which is preferably a pneumaticallyoperated motor or diaphragm valve, is mounted in pipe 15 to control thereturn of pressure fluid from cylinder L to reservoir 13. A constantflow controlvalve 15a may also be installed in pipe 15. Bleed valve 16is preferably normally closed so that upon actuation by suitableactuating fluid, such as air or gas, it will open to permit return offluid from cylinder L through pipe 15 to reservoir 13. Pipe A is fittedwith a normally closed motor valve 18, which when actuated by means ofpneumatic or other pressure fluid, will open to admit power gas intocasing C. A block valve17 may be installed in pipe A between motor valve18 and casinghead H.

The hydraulic actuating system comprising pump 12, reservoir 13,cylinder L and the other elements connected thereto, is employed toeffect reciprocation of upper portion U of the tubing string. Thus, whenpressure fluid is discharged into cylinder L beneath piston R, the upperportion of the tubing string will be elevated toits uppermost positionand will remain in its elevated position so ,long as bleed valve 16stays closed. When bleed valve 16 is opened, pump '12 being stopped,pressure fluid in cylinder L will flow out of the cylinder by gravityassisted by the weight of the tubing imposed through piston R in top ofthe body of pressure fluid in the cylinder and will discharge throughbleed pipe 15 into reservoir 13 under the control of bleed valve 16. Asthe presure fluid is bled from cylinder L, the upper portion U of thetubing string will descend through its own weight. Closing of the bleedvalve 16 will immediately stop the descent of upper portion U. I

Injection valves are so constructed, as will be described more fullyhereinafter, that when upper portion U of the tubing string has beenmoved to its uppermost position, all the valves will be closed and whenupper portion U descends, the valves will open, the lowermost valveopening first and the remaining valves opening successively in theupward or descending direction. When upper portion U is moved upwardlytoward its uppermost position, the valves will close, the uppermostvalve closingfirst and the succeeding valves closing in descendingorder.

Operation of the system is under the control of an automatic controllerE comprising the apparatus enclosed within the block, indicated by thebroken lines in FIG. 1, which will be described more fully herienatter.

As best seen in FIGS. 3 to 6, inclusive, each of the valves 10 comprisesan outer body sleeve 20 concentrically surrounding an inner body sleeve21, the latter extending into the upper end of outer body sleeve 20 andbeing axially reciprocable relative thereto. The lower end of outer bodysleeve 20 is internally threaded at 22 to receive the externally"threaded pin portion 23 of a coupling 24, the lower end of whichdefines an externally threaded pin 25 to be received in the upper end ofone of the nipples G or in the upper end of tubing portion V, dependingupon its location in the tubing string. The upper end portion of innerbody sleeve 21 has an externally threaded pin 26 for connection to thelower socket 27 of a. coupling 23, the upper end of which has aninternally threaded socket 229 for receiving the lower end of a nipple Gor of upper portion U of with each other.

tubing T, again depending upon the particular location of the valve inthe tubing string. A non-rotative, longitudinally slidable connection isprovided between the inner and outer body sleeves by means of a pair ofdiametrically spaced upstanding keys 3tl-30 formed as extensions ofcoupling pin 23 slidably receivable in registering longitudinal slots3131 formed in the lower end of inner body sleeve 21 (FIG. 6).

Beginning a short distance below its upper end, the bore wall 32 of theouter body 20 is undercut for a portion of its length to define adownwardly facing annular shoulder 33 which slopes downwardly andoutwardly to form a valve seat. Inner body 21 is provided at a pointintermediate its ends with an external upwardly facing annular shoulder34 tapered to complement shoulder 33 to form a valve member abutablewith shoulder 33 to provide a metal-to-metal seal between the inner andouter body sleeves when the shoulders are in contact Immediately aboveshoulder 34 inner body sleeve is provided with a short cylindricalenlargement 35 whose diameter is less than that of shoulder 34 but suchas to provide a sliding fit with bore wall 32. The latter has seatedtherein, in an annular recess 36a,

an annular resilient packing 36, such as a conventional O-ring, in aposition to sealingly engage the exterior surface of enlargement 36 whenshoulders 33 are in abutting engagement. Enlargement 35 and packing 36thus form a second or supplemental seal between inner and outer bodysleeves 21 and 26. The length of enlargement 35 is made such that thissupplemental seal will be effected for a short length of relativemovement between the body sleeves in advance of engagement ordisengagement of shoulders 33 and 34. The surface of the portion 37 ofinner body sleeve 20 between enlargement 35 and pin 26 will be madesquare or of other non-round shape (FIG. 5) to provide substantialclearance spaces 38 between inner body sleeve 20 and bore wall 32.

An. annular packing 39 is mounted about inner body sleeve 20 above theupper ends of slots 31 and immediately below shoulder 34 and is securedin place by means of a clamping sleeve 40 held in place by a lock ring41 mounted in the exterior of body sleeve 20. Packing 39 is formed witha depending flexible lip 42 about its exterior adapted to slidablyengage the undercut portion of bore wall 32 and form therewith a checkvalve permitting downward flow of fluid past the lip but sealing tightlywith the bore wall when subjected to fluid pressure from below toprevent upward flow of fluid between the inner and outer body sleeves.

In operation of valves 10, it will be seen that when inner body sleeve21 is moved downwardly relative to outer body sleeve 20, shoulder 34will first dis-engage downwardly from shoulder 33 and when this movementhas continued for an additional short distance, enlargement 35 will movedownwardly past packing 36, thereby opening the annular space betweenthe inner and outer body sleeves to passage of fluid flowing downwardlythrough spaces 38. The fluid thus passing between the body sleeves willflow past the check valve formed by lip 42 and will pass through slots31 in the inner body sleeve into the bore thereof or around the lowerend of inner body sleeve into the bore thereof. Thence, the fluid willflow into the bore of the tubing string and upwardly therethrough intocylinder L above piston R and thence through master valve 19 anddischarge fittings F to storage or other disposal. The open position ofthe valve is illustrated in FIG. 4.

Upward movement of the inner body sleeve in response to upward movementof upper portion U of the tubing string will return the valve to theclosed position shown in FIG. 3. Upward movement of the inner bodysleeve from the open position of FIG. 4 toward the closed position ofFIG. 3, will first bring enlargement 35 into sealing engagement withpacking 3d, effecting an initial seal, after which continued upwardmovement of the inner body sleeve will bring shoulder 34 into seatingengagement against seat shoulder 33 completing the shut-oflf through thevalve.

Automatic controller E includes first and second clockdriven timingwheels 56 and 51, respectively, of generally conventional construction,carrying respective series of timing earns 52 and 53, which cooperatewith related cam followers 54 and 55, respectively, for actuating thevarious control elements at time intervals determined by the relativeposition and arcuate length of the cams, as is conventional in devicesof this character.

Timing wheel 58 controls a first pilot valve, designated generally bythe numeral 56, comprising a casing 57 having inlet and outlet ports 58and 59, respectively, a bleed port 60 and a valve member 61 which ismovable between positions opening and closing communication betweeninlet port 58 and outlet port 59. When valve member 61 is in theposition closing communication between the inlet and outlet ports, bleedport 60 will be open, as seen in FIG. 1. It will be understood that whenvalve member 61 is in the position opening communication between theinlet and outlet ports, it will close bleed port 69. Valve member 61 issecured in pendent position from an intermediate point on a weight bar62, one end of which is pivoted at 63 and the other end of which carriesthe cam follower 54. With this arrangement it will be seen that theweight bar will normally tend to urge valve member 61 into the positionclosing communication between inlet and outlet ports 58 and 59 andopening bleed port 60 and will be moved to the communication-openingposition when cam follower 54- is caused to ride up over one of theearns 52. A conduit 64 connects outlet port 59 to motor 16a of bleedvalve 16. A pipe 65 connected to a suitable source of pneumatic fluid,such as high pressure gas or air (not shown) delivers such fluid througha trap 66 and thence through a line 67 to inlet port 58. A high pressureregulator 68 and a low pressure regulator 69 may be interposed in line67 to step down the pressure of the penumatic fluid to that required foroperation of pilot valve 56.

A second pilot valve, designated generally by the numeral 70, iscontrolled by timing wheel 51. Pilot valve 70 is substantially identicalin form and operation to pilot valve 56, comprising a casing 71 havingan inlet port 72, an outlet port 73, a bleed port 74, and a valve member75 movable in casing 71 between positions opening and closingcommunication between the inlet and outlet ports. Valve member 75 isdependently supported from an intermediate point on a weight bar 76, oneend of which is pivoted at 77 and the other end carries cam follower 55.As in the case of pilot valve 56, weight bar 76 manually urges valvemember 75 into the communication-closing position, shown in FIG. 1, butmoves the valve member to the communication-open position when camfollower 55 is caused to ride up and over a cam 53. A line 78 connectsinlet port 72 to line 67 at a point between pilot valve 56 and lowpressure regulator 69 so that both pilot valves will be supplied withpneumatic pressure fluid from a common source and at a uniform pressure.Conduit 79 connects outlet port 73 to pneumatic motor 12b.

A third pilot valve, designated generally by the numeral 80, controlsthe operation of motor valve 18 and comprises a casing 81 having aninlet port 82, an outlet port 83, a bleed port 84, and a valve member 85movable between positions opening and closing communication between theinlet and outlet ports. Valve member 85 is operatively connected to apivoted lever 86 having an operative connection to one end of aconventional Bourdon tube 87, the other end of which is operativelyconnected by means of a tube 87a to gas supply pipe A at a pointdownstream of motor valve 18. Expansion and contraction of Bourdon tube87 serves to move valve A line 88 connects inlet port 82 to line 67 at apoint between high and low pressure regulators 68 and 69, and a separatelow pressure regulator 89 may be mounted in line 88 to regulate thepressure of the pneumatic fluid going to pilot valve 80. A line 90connects outlet port 83 to the motor 18a of motor valve 18. A conduit 91connects into line 90 and leads into one end of a cylinder 92 whichenclose a shift piston 93 which projects through the opposite end ofcylinder 92 for engagement with a cam lug 94 secured to weight bar 62 ata point between pivot 63 and valve member 61, the arrangement being suchthat when piston 93 is moved outwardly of cylinder 92 (to the right inFIG. 1) the pressure of the piston on cam lug 94 will urge weight bar 62upwardly about pivot 6.3 causing valve member 61 to shift from theposition closing communication between inlet port 58 and outlet port 59to the position open such communication. The outward movement of piston93 is resisted by a coil spring 95 suitably mounted between the pistonand cylinder 92.

The above-described system operates in the following manner: It will beassumed that at the beiginning of a cycle, piston R will be in itsuppermost position, at which upper tubing portion U will have beenelevated sufiiciently so that all of the valves 10 will be in theirclosed positions. Timing wheel 50 will operate through engagement of oneof its earns 52 with follower 54 to actuate pilot valve 56 by raisingweight bar 62 so as to shift valve member 61 to its upper positionopening inlet port 58 to communication with outlet port 59 while closingvent port 60. Actuating gas from line 67 will then flow through line 64to motor 16a of bleed valve 16, opening the latter and allowinghydraulic fluid to bleed back from cylinder L through pipes 11 and 15into reservoir 13. As the hydraulic fluid bleeds back into thereservoir, piston R lowers slowly thereby lowering upper tubing portionU which causes valve 10 to open. The lowermost valve 10 will open first,the other opening in ascending order as tubing portion U continues todescend.

A fluid level Z will normally be present in the casing annulus whichwill ordinarily submerge one or more of the injection valves, and thecasing above fluid level Z will be filled with power gas under pressurepreviously supplied through pipe A. As the valves open in response tothe lowering of tubing portion U, the first to open above fluid level Zwill start to pass gas into the tubing string to lift the well fluidtherein to the surface. The passage of gas from the casing annulus willcause a pressure drop in the casing which will be immediately sensed byBourdon tube 87 which will then operate to actuate pilot valve by movingvalve member to the open position placing ports 82 and 83 incommunication. This will permit actuating gas to flow from pipe 88 intopipe opening motor valve 18 and thereby permitting power gas to flowinto the casing. At the same time, some of the actuating gas will flowthrough pipe 91 into cylinder 92 and cause piston 93, acting through camlug 94, to shift weight bar 62 in a direction to move pilot valve member61 to the position closing communication between ports 58 and 59 (FIG.*1) and stopping the flow of actuating gas to motor 160, therebyallowing bleed valve 16 to close and immediately stopping furtherdescent of the tubing string. The tubing string will thus remain open atthe first valve which has admitted the gas and lifting gas will continueto feed into the tubing from the casing annulus. After a pre-determinedtime interval, as set on timing wheel 51, pilot valve 78 is actuated,valve member 75 being thereby moved to the position openingcommunication between ports 72 and 73 and passing actuating gas frompipe 78 to pipe 79 and thence to pump motor 12b. The latter will startpump 12 which will begin pumping pressure fluid from reservoir 13through pipe 11 into cylinder L which will raise piston R and tubingportion U. As the latter ascends, the injection valves will start toclose in descending order from the uppermost valve. When the operatingvalve closes, the pressure in the casing starts to build up.

This will be immediately sensed by Bourdon tube 87 which will operate toclose pilot valve 8&3 causing motor valve 18 to shut off further flow ofgas to the casing. The cycle is completed when piston R reaches the topof its stroke. At the same time that pilot valve 8%) is closed,actuating gas will be cut off from shift piston 93, relieving thepressure on cam lug 94- and leaving valve member 61 in position forupward movement in response to the contact of the next timing cam 52with cam follower 54 to initiate repetition of the cycle.

From the foregoing, it will be seen that the abovedescribed systemcomprises the combination with a series of telescoping-type valves in atubing string, of a control arrangement by which a well will beautomatically unloaded to an operating valve and which will, during eachcycle, seek out the lowermost point at which the gas may be injectedinto the tubing. The described system may be used in both anintermitting well with a low producing rate, or in a continuous flowinstallation which produces large quantities of fluid. The controlsystem described will automatically seek out the most efiicientoperating point at predetermined time intervals which may e set into thecycle timers of the automatic controller. Where the system is employedin an intermitting gas lift installation which requires intermittentoperation, the location of the most eflicient operating point iseflected at the beginning of each cycle. In the case of a continuousflow installation, the time cycle controller is set to hunt, at periodicintervals, the lowermost injection point. This time may be set by theoperator according to the wells producing characteristics.

Whether the Well is an intermittent well or a constant flow well, thesame sequence of operations is employed, except that in the case of thecontinuous flow installation, timer 51'is set so as not to start withina short period after the input gas commences t flow into the casing.Instead, the time is set so that the gas will be allowed to flowcontinuously into the casing and the well permitted to operate onconstant flow for a major portion of each day. Timer 51 Will then beemployed to periodically search for the best operating level. This isdone by setting timer 51 to permit pump 12 to start at somepredetermined interval after the well has been flowing for some time,perhaps several hours, in order to move piston Rto the top of itsstroke. Thereupon, after a pre-determined and usually very short time,the above-described sequence of steps starting with actuation of pilotvalve 56 is begun. This continuous flow arrangement is then comparableto an intermitting flow which is set to cycle perhaps only once or twiceper day.

By means of the above-described arrangement, not only is the operationof the well conducted automatically, but the operation will be conductedat maximum efliciency with respect to the use of lifting gas, therebygreatly reducing any gas wastage.

It will be evident that various means other than that described abovemay be used to control the flow of gas into the Well and the operationof the lift piston for controlling the valve settings.

FIG. 7 illustrates, diagrammatically, another modification which may beemployed in lieu of the Bourdon tube 87 and motor valve 15. In tlr smodification, a swing check valve ltlll is substituted for motor valve18, the valve being arranged so that its flapper element ltll will swingopen when the downstream pressure falls. A sensing element 102 of anyconventional design, which is adapted to sense the movement of flapperelement 1M, is employed to connect the latter to valve member 85 ofpilot valve 869. With this arrangement, when gas begins to flow from theeasing into the tubing, the resultant drop in pressure in the casingwill cause flapper element 161 to swing to the open position allowinggas to flow toward the well. The movement of the flapper will betransmitted to sensing element 1492 which will cause valve member 85 tomove to the open position, causing shift piston Q3 to be actuated inexactly the same manner as previously described.

It will be understood that numerous arrangements, which well-known, maybe employed to respond tothe dropin pressure in the casing in order toactuate the controller. These may include, in addition to the Bourdontube and the check valve-controlled pilot valves previously described,bellows-controlled pilot valves, differential pressure devices, and thelike.

Also, other arrangements than that described may be employed toterminate each cycle. In cases Where'the casingholds a large volume ofgas, the volume of gas injected into the tubing which will be sufiicientto drop the casing pressure enough to actuate control valve 13 and shiftpiston 93 will also be suflicient to lift the fluid in the flow stringto the surface. In such cases, the second timing wheel 51 and its pilotmay be eliminated and line 79 connected to line Q1. With thisarrangement, upon the drop in pressure in the casing, which moves shiftpiston 93 to close bleedvalve 16, pump 12 will be started and will raisethe tubing to close the operating valve.

Another alternative is the provision of a pressure sensing element, suchas another Bourdon tube, connected to the flow tubing. This element,upon sensing an increase in tubing pressure produced by the rise of theproduction fluid to the surface, could be connected to the pilot systemin any suitable manner, which will be obvious to those skilled in thisart, to activate pump 12 or to override timer 5]..

Many other alterations and modifications will be evi dent to thoseskilled in the art and are deemed to be within the scope of the appendedclaims without departing from the spirit of this invention.

What I claim and desire to secure by Letters Patent is:

1. In a gas lift system for wells having a casing,-a conduit forsupplying lifting gas under pressure to the interior of the casing, aflow pipe string inside the casing comprising a lower section anchoredagainst movement and an upper section reciprocable relative to the lowersection, telescoping coupling means connecting said sections, saidcoupling means defining port means adapted to open and close in responseto reciprocation of said upper section, fluid pressure-actuated meansconnected to said upper section for reciprocating the same, firsttime-responsive means operably connected to the fluid-actuated means toperiodically cause said upper section to move downwardly to open saidport means to thereby admit lifting gas into the flow pipe string fromthe casing, means operable in response to the resulting pressure drop inthe casing to hold said upper pipe string section in said portopeningposition and to cause gas to flow from said conduit into the casing, andsecond time-responsive means operable periodically'to cause said uppersection of the pipe string to move upwardly to the port-closingposition.

2. In a gas lift system according to claim 1, wherein said fluidpressure-actuated means includes a cylinder enclosing the upper end ofthe upper section of said pipe string, a piston mounted about said upperend for reciprocating the same in said cylinder, and means for supplyingpressure fluid to said cylinder.

3. In a gas lift system according to claim 2, wherein saidlast-mentioned means comprises a pressure fluid reservoir, a dischargeconduit having a pump therein for delivering pressure fluid from saidreservoir to said cylinder, a return conduit from said cylinder to saidreservoir, and a bleed valve in said return conduit operably connectedto said 1 first time-responsive means.

4. In a gas lift system for wells having a casing, a conduit forsupplying lifting gas under pressure to the interior of the casing, aflow pipe string inside the casing comprising a lower section anchoredagainst movement and an upper section reciprocable relative to the lowersection, a plurality of vertically spaced telescoping cou pling meansconnecting said sections, each of said cou pling means includingrelatively movable portions defining flow ports adapted to open andclose in response to reciprocation of said upper section, the severalflow ports being arranged to open sequentially in ascending order inresponse to downward movement of said upper section and to closesequentially in descending order in response to upward movement of saidupper section, fluid-pressure actuated means connected to said uppersection for reciprocating the same, a first time-responsive meansoperable to periodically activate said fluid-pressure actuated means tocause said upper section to descend to a position opening that flow portwhich will first admit lifting gas into the tubing string from thecasing, flow-control means in said conduit operable in response to theresulting pressure drop in the casing to admit lifting gas from saidconduit into the casing, a pressure-responsive means operably connectedto said first time-actuated control means and operable in response tosaid pressure drop to stop the descent of said upper section at saidposition to hold said flow port in the open position, and a secondtime-responsive means operable at a pre-determined interval afteractuation of said first time-responsive control means to activate saidfluid-pressure actuated means to move said upper section upwardly to aposition closing said port means to thereby stop admission of gas intothe flow pipe string, and into the casing.

5. In a gas lift system according to claim 4, wherein saidfluid-pressure actuated means includes a cylinder enclosing the upperend of the upper section of said pipe string, a piston mounted aboutsaid upper end for reciprocating the same in said cylinder, and meansfor supplying pressure fluid to said cylinder.

6. in a gas lift system according to claim 5, wherein saidlast-mentioned means comprises a pressure fluid reservoir, a dischargeconduit having a pump therein for delivering pressure fluid from saidreservoir to said cylinder, 21 return conduit from said cylinder to saidreservoir, and a bleed valve in said return conduit operably connectedto said first time-responsive means.

7. In a gas lift system for wells having a casing, a conduit forsupplying lifting gas under pressures to the interior of the casing, anda control valve in the conduit, a flow pipe string inside the casing andcomprising a lower section anchored against movement and an uppersection reciprocable relative to the lower section, telescoping couplingmeans connecting said sections, said coupling means including port meansadapted to open and close in response to reciprocation of the uppersection of the flow. pipe string relative to the lower section thereof,fluid pressure-actuated means connected to said upper section forreciprocating the same, a first tirne-actuated control means operable toperiodically activate said fluid pressure actuated means to move saidupper section of the flow pipe string to a position opening said portmeans to thereby admit lifting gas into the flow pipe string from saidcasing, a pressure-responsive means operably connected to said controlvalve and to said first control means op eraole in response to a drop inpressure in the casing resulting from said admission of lifting gas intothe flow string to open said control valve to permit flow of gas fromsaid conduit into said casing and to simultaneously actuate said firstcontrol means to maintain said upper section of the flow pipe string inthe position opening said port means, and a second time-actuated controlmeans operable at a pre-determined interval after actuation of saidfirst control means to actuate said fiuid pressureactuated means to movesaid upper section of the flow pipe string to a position closing saidport means to thereby stop admission of gas into the flow pipe stringand permit the pressure in the casing to increase, saidpressureresponsive means being actuated by said pressure increase toclose said control valve.

8. In a gas lift system for wells having a casing, a con duit forsupplying lifting gas under pressure to the interior of the casing, aflow pipe string inside the casing comprising a lower section anchoredagainst movement and an upper section reciprocable relative to the lowersection, telescoping coupling means connecting said sections, saidcoupling means defining a gas injection valve having port means adaptedto open and close in response to reciprocation of said upper section,fluid pressure-actuated means connected to said upper section forreciprocating the same, first time-responsive means operably connectedto the fluid-actuated means to periodically cause said upper section tomove downwardly to a position opening said port means to thereby admitlifting gas into the flow pipe string from the casing, means operable inresponse to the resulting pressure drop in the casing cooperating withsaid fluid pressure-actuated means to stop the downward movement of saidupper section whereby to hold said upper pipe string section in saidport-opening position and to admit lifting gas from said conduit to thecasing, and second time-responsive means operable on said fluidpressure-actuated means after a pre-determined time interval to raisesaid upper section of the pipe string to the portclosing position.

9. In a gas lift system according to claim 8, wherein said gas injectionvalve comprises concentric inner and outer sleeves having spacetherebetween to define flow passage means, an internal annular shoulderin the bore of the outer sleeve, an external annular shoulder on theinner sleeve, said shoulders being abuttable in response to relativelongitudinal movement between the sleeves in one direction to form ametal-to-metal seal between the sleeves to close said passage means, andto separate upon relative movement of the sleeves in the oppositedirection to open said passages, annular packing mounted between thesleeves on one side of said shoulder to form an auxiliary slidable sealbetween the sleeves, and a lip-type flexible seal between the sleeves onthe opposite side of said shoulders to define a one-way check valve forsaid passage means.

References Cited in the file of this patent UNITED STATES PATENTS1,731,694 Wineman Oct. 15, 1929 2,313,066 Hatfield Mar. 9, 19432,405,324 Nixon Aug. 6, 1946 2,416,359 Thompson et al Feb. 25, 1947

1. IN A GAS LIFT SYSTEM FOR WELLS HAVING A CASING, A CONDUIT FORSUPPLYING LIFTING GAS UNDER PRESSURE TO THE INTERIOR OF THE CASING, AFLOW PIPE STRING INSIDE THE CASING COMPRISING A LOWER SECTION ANCHOREDAGAINST MOVEMENT AND AN UPPER SECTION RECIPROCABLE RELATIVE TO THE LOWERSECTION, TELESCOPING COUPLING MEANS CONNECTING SAID SECTIONS, SAIDCOUPLING MEANS DEFINING PORT MEANS ADAPTED TO OPEN AND CLOSE IN RESPONSETO RECIPROCATION OF SAID UPPER SECTION, FLUID PRESSURE-ACTUATED MEANSCONNECTED TO SAID UPPER SECTION FOR RECIPROCATING THE SAME, FIRSTTIME-RESPONSIVE MEANS OPERABLY CONNECTED TO THE FLUID-ACTUATED MEANS TOPERIODICALLY CAUSE SAID UPPER SECTION TO MOVE DOWNWARDLY TO OPEN SAIDPORT MEANS TO THEREBY ADMIT LIFTING GAS INTO THE FLOW PIPE STRING FROMTHE CASING, MEANS OPERABLE IN RESPONSE TO THE RESULTING PRESSURE DROP INTHE CASING TO HOLD SAID UPPER PIPE STRING SECTION IN SAID PORTOPENINGPOSITION AND TO CAUSE GAS TO FLOW FROM SAID CONDUIT INTO THE CASING, ANDSECOND TIME-RESPONSIVE MEANS OPERABLE PERIODICALLY TO CAUSE SAID UPPERSECTION OF THE PIPE STRING TO MOVE UPWARDLY TO THE PORT-CLOSINGPOSITION.